Background: Staphylococcus aureus is a frequent cause of hospital and community-associated infections on a global scale. This pathogen is responsible for causing an extensive range of diseases and sometimes create biofilms for their survival. Biofilm formation, leads to difficulty in treatment with antibiotics and antibiotic resistance which is another rising concern in health centers. Some S. aureus virulence factors encode on the core genome, such as alpha-toxin and phenol-soluble modulins (PSMs), which are produced by nearly all strains. Objectives: There is no information about the expression of PSM A gene in clinical isolates of biofilm-producing S. aureus in Iran. This study was performed on clinical samples to determine the prevalence and expression of PSM A gene in biofilm-producing S. aureus clinical isolates. Methods: The clinical samples were collected and examined for S. aureus by microbiological and biochemical tests. Then, the biofilm formation in S. aureus isolates was detected by microtiter plate. Finally, the expression of PSM A was determined using SYBR Green real-time PCR. Results: From a total of 60 isolates of S. aureus, 47 strains (78.3%) had ability of biofilm formation and the others were negative for biofilm formation. Real-time PCR testing showed that 100% of the strains were positive for biofilms and PSM A genes. The results of phenotypic and genotypic tests of biofilm were closely related to each other and the expression of PSM A gene was 80%. It was found that 100% of strains were biofilm producing and PSM A gene was present in 78.3% (47 strains) of them. Conclusions: The prevalence of biofilm production in S. aureus strains isolated from clinical samples was high, so it is highly important to monitor the prevalence of these organisms in hospitals and community as well as their antimicrobial resistance.

Backgrounds: Staphylococcus aureus is one of the major causes of nosocomial infections. Biofilm formation is an important virulence factor of S. aureus, leading to its high resistance to antibiotics and evasion from host defenses. This study aimed to assess the prevalence and antimicrobial resistance profile of biofilm-producing S. aureus strains and characterize genes involved in biofilm formation. Materials & Methods: A total of 79 S. aureus strains were isolated from 1000 clinical samples and characterized using phenotypic, biochemical, and molecular tests. The biofilm production ability of isolates was examined using the microtiter assay. Moreover, the expression of genes involved in biofilm production (psm A and psm B) was screened using real-time PCR. Finally, antibiotic susceptibility testing was done using the Kirby-Bauer method and interpreted according to the CLSI M100 standard. Findings: Out of 79 S. aureus isolates, 43 (54.4%) isolates were strong biofilm producers, 21 (26.6%) isolates were weak biofilm producers, and 15 (19%) isolates were non-adhesive. The results of real-time PCR showed that 55 (86%), 60 (93.7%), and 46 (58.2%) isolates were positive for psm A, psm B, and both genes, respectively. The results of antibiotic susceptibility testing showed that all the isolates were resistant to two or more antibiotics. Conclusion:The high prevalence of biofilm-forming S. aureus strains in hospital environments could be a major health challenge with serious outcomes for hospitalized patients. Thus, it is necessary to disinfect hospital environments to reduce the risk of infection and spread of these microorganisms.

Background and Objectives: Staphylococcus aureus is one of the most common causes of morbidity and mortality among intensive care unit (ICU) patients. Nasal carriage is one of the main routs of S. aureus transmission between hospital personnel and patients. The objective of this study was to evaluate the efficacy of mupirocin ointment in eradication of nasal carriage of S. aureus in the ICU staff and patients of Panje-Azar hospital in Gorgan, Iran. Methods: In the first three months of the study (January to March), the prevalence of S. aureus among ICU patients was determined by routine microbiological and biochemical testing. Nasal samples were taken from ICU staff and all patients recently admitted to the ICU. Mupirocin nasal ointment (2%) was applied for treatment of S. aureus nasal carriers. Posttreatment sampling was done after five weeks. During the next three months, the presence of S. aureus and rate of resistance to methicillin was evaluated in new patients admitted to the ICU using the method used previously. Results: Of 60 samples from the ICU staff, seven (11.7%) samples were positive for S. aureus. Moreover, of 240 samples from the ICU patients, two samples were found as S. aureus-positive. Of the nine S. aureus-positive isolates, only two (22.2%) were methicillinresistant S. aureus (MRSA). In the pre-intervention sampling, only five samples (2.8%) were identified as S. aureus, two of which were MRSA. However, treatment with mupirocin ointment eradicated nasal carriage of S. aureus and no isolate was found after the intervention. Conclusion: Our finding showed that mupirocin nasal ointment is highly effective in eradication of S. aureus nasal carriage and subsequently contribute to reduction in frequency of nosocomial infections in the ICU.

Background and Objectives: Staphylococcus aureus is a common cause of hospital-and community-acquired infections in the world. This microorganism causes a wide range of diseases, and biofilm formation is as an important mechanism for its virulence. Alpha-toxin and phenol-soluble modulins (PSMs) are among the main factors involved in the biofilm formation by S. aureus. The aim of this study was to detect PSM B gene among biofilm-forming S. aureus clinical isolates from hospitalized patients at the 5 th Azar Hospital in Gorgan, Iran. Methods: Clinical specimens were collected and examined for presence of S. aureus using conventional microbiological and biochemical tests. Then, biofilm formation ability of S. aureus isolates was evaluated using the microtiter plate assay. In addition, presence of the PSM B gene was assessed using real-time PCR. Results: Of 1,800 clinical isolates, 60 (3.3%) were identified as S. aureus. Of these isolates, 47 (78.3%) were positive for biofilm formation. The PSM B gene was present in all biofilm-forming isolates. Results of the phenotypic and genotypic biofilm tests were closely linked and the rate of PSM B expression was 80%. Conclusion: The prevalence of biofilm-producing S. aureus clinical isolates from patients hospitalized in the 5 th Azar hospital of Gorgan (Iran) is relatively high, which could pose a serious challenge. Therefore, regular surveillance of biofilm formation in S. aureus isolates and their antimicrobial resistance profiles is highly recommended.